In recent decades there has been a marked decline in morbidity and mortality from coronary heart disease (CHD) in the US. But the strength of this trend varies across demographic groups. Those of low socioeconomic status (SES) continue to develop, and die from, CHD at rates more typical of the 1970's. Most research on the origins of these disparities focuses on middle stages of the lifespan, when CHD manifests clinically. While this research has been fruitful, shifting the focus towards earlier life stages could yield valuabl insights. Many pathogenic mechanisms that give rise to CHD begin in childhood, and by adolescence increasing numbers of American youth display risk factors for and preclinical signs of CHD, which themselves pattern by SES. Despite these findings, relatively little attention has been directed towards early CHD disparities. We know little about why they emerge and how they unfold developmentally. To address these questions, we propose a prospective, multilevel study of 250 youth from economically diverse backgrounds. Subjects will be enrolled during eighth grade and reassessed in tenth grade. Drawing on hypotheses from a recently developed conceptual framework, the study poses three questions about SES disparities in immunologic, neural, and psychosocial development, and the implications for early CHD risk. First, we ask whether SES relates to maturation patterns in the immune system, with a focus on inflammatory processes that underlie CHD. We expect low-SES youth to display a multilayer inflammatory phenotype, which manifests at the genomic, cellular, and systemic levels of analyses. Second, we ask whether SES relates to maturation patterns in the brain's corticolimbic and corticostriatal circuitries, and thereby give rise to behavioral proclivities that heighten CHD risk. Using high-dimensional structural imaging and diffusion tensor imaging, we expect low SES to be associated with disparities in grey- and white-matter development in these circuitries. These disparities should, in turn, presage CHD-relevant behavioral proclivities, including threat vigilance, social turmoil, poor self-regulation, and unhealthy lifestyles. Finally, noting that som low-SES youth have positive health outcomes, we explore characteristics and experiences that bend the normative demographic curve. We expect that lower-SES youth who encounter positive social influences - specifically role models and high maternal warmth - will develop a suite of personal resources - trust, emotion regulation skills, and self-esteem - that help them navigate the challenges of high school and low-SES life more broadly. Those resources will shift low-SES youth off their expected risk trajectory, resulting in immune and neural patterns similar to higher-SES youth.